Impact response and mechanical behavior of 3-D ceramic matrix composites

This paper examines the impact response, compressive strength, and flexural strength of three-dimensional carbon fiber reinforced ceramics. The composite was fabricated by combination of the pressure infiltration method and sol–gel processing, using the mixture of silica sol and alumina particles. The effects of sol viscosity on impact response and flexural strength, and infiltration pressure on compressive strength are investigated. Impact tests were carried out using an Izod impact testing machine. It is found that impact energy of the specimens increases linearly with sol viscosity. The sol viscosity affects impact response by two factors, interfacial strength and volume fraction of silica. Higher sol viscosity leads to weaker interface and more residual silica, resulting in higher impact energy. Flexural strength decreases with sol viscosity according to an exponential decay function because higher viscosity leads to weak interface as well as lower flexural strength. Compressive strength increases with infiltration pressure, which follows a parabolic function. Higher infiltration pressure enhances infiltration of the mixture, resulting in dense matrix and strong interface. As a result, the composite shows a higher compressive strength due to less buckling of longitudinal fibers strongly confined by neighboring dense matrix and transverse fiber bundles. The compressive stress-strain history has been examined and related to how the specimens respond to the compression.